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04 x
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Discussion Starter · #1 ·
I love my Subaru to death and recently the Subie's been acting up. After some hard acceleration my car started to shudder and stutter. The check engine light came on during this. I read the codes which were p303 and p303pd. The car runs fine when I drive like a grandma but any hard acceleration the car just dies. I also noticed the car has a hard time getting into gear when I accelerate now and then. I believe its a cracked spark plug but I'm not quite sure.


PLEASE HELP!!!
 

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2005 Base 2.5x foz
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896 Posts
How much mechanical experience do you have? I would check the power and ground to the ignition coils. Make sure they function properly. If they do, pull your plugs and check them out. If the plugs are good look into the fuel injector to make sure it is working.
All of this requires some know how and a couple tools... But it's not to hard.
As for the trans issue, does it occur only when the engine failure does?
 

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04 x
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71 Posts
Discussion Starter · #4 ·
I have 140,000 and I've been pretty good about the maintenance schedule. I also forgot to add my fuel economy has dropped significantly. Each tank will only last me up to 200 miles.


And to answer subie roo's question the trans issue has started ever since the stuttering started.
 

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2016 & 2018 2.5i Premium CVT
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19,781 Posts
"Dying" sounds like an overstatement! Anything in the circuit from the coil to the plug in cylinder #3 could be causing those symptoms, and it shouldn't be major thing to fix. You can test a good bit of the stuff by substitution with a nearby cylinder.

My P030x from last year produced similar symptoms. Itwas caused by a broken connection within the plug boot.
 

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2007 Forester Sports XT 4EAT
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41,735 Posts
If the engine is running poorly, the transmission is going to be affected, especially if it's a 4EAT.

Okay, with 140K miles, your timing belt was changed at around 105K & your sparkplugs should have been changed at least twice. If the sparkplug wires weren't changed the last time, they could be failing. Then there's the coil pack, which could be failing, or the connections to it could be corroded.

Just guessing of course, but that should give you some areas to check. :wink:

Bobby...

My MODding Journal
 

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1999 Forester
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52 Posts
the codes are for o2 sensors are they not?
happened to me changed out the o2 sensor in bank on (the one on the header)
reset the computer (unplug the battery for half hour)
and everythings been fine since

when the o2 sensor goes out it messes up the fuel injection
so when you get on it hard it runs way rich

hope this helps
 

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2007 Forester Sports XT 4EAT
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Front O2 sensor? Possible & they do start failing before they drop a code. Still, I'd expect to see a P0420 from the rear O2 sensor, if the engine was running way rich. :wink:

Bobby...

My MODding Journal
 

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2015 Forester X 6MT 6-Gear Manual
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1,373 Posts
Work on the ignition. TODAY. The engine would run OK with a bad o2 sensor. His cats will be dead soon (if not already) if he doesnt fix the bad cyl RIGHT NOW.
 

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Yes, the symptoms exactly match my plug cable problem of last year. As for the front O2 sensor, the only thing that made me notice it when it went bad was the CEL. Car felt quite normal. And though there is some confusion as to the CEL code you got, putting 2 and 2 together sure comes up with something like P0303, which means bad spark in cylinder #3.
 

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04 x
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Discussion Starter · #15 ·
Thanks for the reply's guys! To be honest, I don't think the spark plugs have been changed on this car once which is pretty bad I know. Is there anything tips you guys have on replacing spark plugs?
 

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2007 Forester Sports XT 4EAT
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Thanks for the reply's guys! To be honest, I don't think the spark plugs have been changed on this car once which is pretty bad I know. Is there anything tips you guys have on replacing spark plugs?
Here you go. http://www.subaruforester.org/vbulletin/f66/n-spark-plug-replacement-anal-55431/#post615927

A dealership will charge you around a $100 for labor to install the sparkplugs. :wink:

How about the timing belt & associated parts? :confused: If you loose the timing belt, you'll most likely be looking at a new engine! :icon_eek:

Bobby...

My MODding Journal
 
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